Fujitsu asu18c1 mini split ah

Unit won't come on -
Upon arrival found 3 amp fuse that is connected to filter circuit board to be bad. Client stated the blower was running slow before the unit quit.
Need schematic to locate short and determine what part or parts need to be replaced.

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If this is a mini split ductless there is a control wire with 3-4 wires inside (normally red, white, blue and green) that is connected from the outdoor unit to the indoor unit. This wire feeds voltage from the o.d. unit to the I.d. unit. If all connections at the o.d. unit are good, then check for voltage at these connections at the o.d. unit. If no power at these connections then a circuit board has faulted. Call a tech. and have a tech support number ready (1-800#) in case your service tech don't have it.

Power off at the isolator for 10 mins then switch back on and try again. If error code persists, then it is most likely the controller in the outdoor unit.
Excessive voltage of DC voltage on PFC circuit in inverter PCB is detected, or the excessive current in the circuit is detected.
> Permanent stop.
[Diagnosis Point]
Controller PCB defective (Refer to after mentioned "PFC circuit diagnosis")

Split system Air conditioners are very often on two or more separate breakers, with a control voltage (24vac commonly) connecting their operation. the condensor unit and out-door fan generally on a 220 vc 'paired' breaker, possibly a quick disconnect near the unit with fuses inside, or an independant breaker pair, and the evaporator unit with INDOOR fan on a 110 or 220 vac breaker.

switch the fan to 'ON' at the thermostat... this is the midpoint of the system electrically. If the fan comes on check for voltage at the condensor unit. a check to see if the thermostat is the problem... remove the thermostat and connect the red, green and either the white or yellow wires (not both) if you chose white you should have heat...yellow AC...

most split system AC have a small buss fuse on the control circuit board of the indoor unit. looks like a glass tube with metal caps held by metal clips. In 40+ yrs experience I have found it is more likely one or both of the 30 amp buss fuses near the outdoor unit (replace both even if one is still ok) or a 30 amp breaker in the quick disconnect box.
In many systems the control voltage to the thermostat derives from a transformer in the outdoor unit... it could be as simple as a broken wire. Without a full diagnostic, a complete description of the unit ( AC or heat pump, etc) this is all speculation

It sound like you have a direct short in the compressor ,Usually it means you have a bad compressor,but sometimes it could be a loose wire or bad outdoor motor. Ive installed about 10 of these units and still have yet to have a bad compressor.It could also be a bad circuit board in the outdoor unit.I wish I could narrow it down better but thats my best guess!Thanks ---Nate

Check the disconnect switch and make sure that both the fuses are good and not shot. If one is shot then the system wont work. There are two fuse. Also be careful due to you will be working around 210 volts

it will have to be whatever part is in that circuit, if it's the blower you need to ohm it out and check the bearings and capacitor. if there is a wiring diagram it will help you determine what is in that circuit.